Hi Cartalk community! I am honored, as much as one can be, to share my car problems with other gearheads like you - not that such a quality is desirable (my attempt at self-deprecating humor).
Car: 1995 Corolla 1.8L automatic
Symptom: misfires around 3000-3500 RPM only when warm.
So before you read further or give a suggestion, I have replaced the following:
Spark plugs, wires, cap, and rotor
Ignition coil
Fuel filter
poured some quality fuel system cleaner into the gas tank
The car stutters when accelerating in any gear hard enough to reach the engine speed that the misfire occurs at. It doesn’t backfire, it just misses… I am confused since so many of the misfire issues I know about that are RPM specific are spark-related.
I have considered cleaning the injectors, but don’t want to go through the hassle to remove and have them cleaned unless I really have to.
Do you think my hunch on the injectors is correct?
Something else?
The problem might be a lazy O2 sensor. The O2 sensor doesn’t feed the computer information until the engine is up to operating temperature for proper fuel mixture… Because the engine management system is the OBDI, the Check Engine light might not come on for a lazy O2 sensor. But there is a way to test for a lazy O2 sensor.
Remove the sensor from the vehicle and place it into a vice.
Connect a volt/ohm meter set on the 2 VDC scale, positive lead to the signal out terminal on the O2 sensor connector and the negative lead to the body of the O2 sensor.
With a propane torch, apply the flame to the tip of the O2 sensor while observing the voltage on the meter. The voltage should smoothly rise to close to 1 VDC. And when the flame is removed the voltage should smoothly drop to close to 0 VDC. If the voltage acts erratic when the flame is applied or removed the problem is with the O2 sensor.